Methods and rail supports for additive manufacturing

ABSTRACT

The present disclosure generally relates to methods for additive manufacturing (AM) that utilize rail support structures in the process of building objects, as well as novel rail support structures to be used within these AM processes. The rail support structures include a plurality of substantially parallel vertical walls, each wall extending substantially parallel to a direction from the first side to the second side. Adjacent walls of the plurality of substantially parallel vertical walls are separated by a portion of unfused powder. An object is formed above the plurality of substantially parallel vertical walls.

The present disclosure generally relates to methods for additivemanufacturing (AM) that utilize support structures in the process ofbuilding objects, as well as novel support structures to be used withinthese AM processes.

BACKGROUND

AM processes generally involve the buildup of one or more materials tomake a net or near net shape (NNS) object, in contrast to subtractivemanufacturing methods. Though “additive manufacturing” is an industrystandard term (ASTM F2792), AM encompasses various manufacturing andprototyping techniques known under a variety of names, includingfreeform fabrication, 3D printing, rapid prototyping/tooling, etc. AMtechniques are capable of fabricating complex components from a widevariety of materials. Generally, a freestanding object can be fabricatedfrom a computer aided design (CAD) model. A particular type of AMprocess uses an energy beam, for example, an electron beam orelectromagnetic radiation such as a laser beam, to sinter or melt apowder material, creating a solid three-dimensional object in whichparticles of the powder material are bonded together. Different materialsystems, for example, engineering plastics, thermoplastic elastomers,metals, and ceramics are in use. Laser sintering or melting is a notableAM process for rapid fabrication of functional prototypes and tools.Applications include direct manufacturing of complex workpieces,patterns for investment casting, metal molds for injection molding anddie casting, and molds and cores for sand casting. Fabrication ofprototype objects to enhance communication and testing of conceptsduring the design cycle are other common usages of AM processes.

Selective laser sintering, direct laser sintering, selective lasermelting, and direct laser melting are common industry terms used torefer to producing three-dimensional (3D) objects by using a laser beamto sinter or melt a fine powder. For example, U.S. Pat. No. 4,863,538and U.S. Pat. No. 5,460,758 describe conventional laser sinteringtechniques. More accurately, sintering entails fusing (agglomerating)particles of a powder at a temperature below the melting point of thepowder material, whereas melting entails fully melting particles of apowder to form a solid homogeneous mass. The physical processesassociated with laser sintering or laser melting include heat transferto a powder material and then either sintering or melting the powdermaterial. Although the laser sintering and melting processes can beapplied to a broad range of powder materials, the scientific andtechnical aspects of the production route, for example, sintering ormelting rate and the effects of processing parameters on themicrostructural evolution during the layer manufacturing process havenot been well understood. This method of fabrication is accompanied bymultiple modes of heat, mass and momentum transfer, and chemicalreactions that make the process very complex.

FIG. 1 is schematic diagram showing a cross-sectional view of anexemplary conventional system 100 for direct metal laser sintering(DMLS) or direct metal laser melting (DMLM). The apparatus 100 buildsobjects, for example, the part 122, in a layer-by-layer manner bysintering or melting a powder material (not shown) using an energy beam136 generated by a source such as a laser 120. The powder to be meltedby the energy beam is supplied by reservoir 126 and spread evenly over abuild plate 114 using a recoater arm 116 travelling in direction 134 tomaintain the powder at a level 118 and remove excess powder materialextending above the powder level 118 to waste container 128. The energybeam 136 sinters or melts a cross sectional layer of the object beingbuilt under control of the galvo scanner 132. The build plate 114 islowered and another layer of powder is spread over the build plate andobject being built, followed by successive melting/sintering of thepowder by the laser 120. The process is repeated until the part 122 iscompletely built up from the melted/sintered powder material. The laser120 may be controlled by a computer system including a processor and amemory. The computer system may determine a scan pattern for each layerand control laser 120 to irradiate the powder material according to thescan pattern. After fabrication of the part 122 is complete, variouspost-processing procedures may be applied to the part 122. Postprocessing procedures include removal of access powder by, for example,blowing or vacuuming. Other post processing procedures include a stressrelease process. Additionally, thermal and chemical post processingprocedures can be used to finish the part 122.

The apparatus 100 is controlled by a computer executing a controlprogram. For example, the apparatus 100 includes a processor (e.g., amicroprocessor) executing firmware, an operating system, or othersoftware that provides an interface between the apparatus 100 and anoperator. The computer receives, as input, a three dimensional model ofthe object to be formed. For example, the three dimensional model isgenerated using a computer aided design (CAD) program. The computeranalyzes the model and proposes a tool path for each object within themodel. The operator may define or adjust various parameters of the scanpattern such as power, speed, and spacing, but generally does notprogram the tool path directly.

FIG. 2 illustrates a plan view of a conventional support structure 220used to vertically support a portion of an object 210. The supportstructure 220 is a matrix support including cross hatching (e.g., scanlines) forming a series of perpendicular vertical walls. The areabetween the platform 114 and an overhanging portion of the object may befilled with such matrix support, which may provide a low densitystructure for supporting the overhanging portion as it is built. In anaspect, a matrix support may be automatically generated for an object tosupport any bottom surface of the object that is not connected to theplatform 114. For example, the MAGICS™ software from Materialise NV maygenerate matrix supports for the object within a CAD model.

The present inventors have discovered that as the additive manufacturingprocess described above is adapted to larger dimensioned parts,difficulties arise for matrix supports. For example, as the size of theadditive manufacturing apparatus is increased to accommodate largerbuilds, lateral forces exerted by the recoater arm on the object andsupports also increases. For example, the recoater arm 116 may directlycontact the support if warping has occurred due to uneven thermaldissipation. Additionally, as the recoater arm pushes powder, the powdermay exert lateral forces on the matrix support. Because the matrixsupports include perpendicular walls, there is always a surface of thesupport that is oriented transverse to the recoater direction. The cellsformed by the matrix support may retain powder such that the lateralforces are applied to the matrix support through the powder. Suchtransverse surfaces are prone to tipping, bending, or other deformationsdue to the lateral forces exerted by the recoater arm 116.

In view of the above, it can be appreciated that there are problems,shortcomings or disadvantages associated with AM techniques, and that itwould be desirable if improved methods of supporting objects and supportstructures were available.

SUMMARY

The following presents a simplified summary of one or more aspects ofthe invention in order to provide a basic understanding of such aspects.This summary is not an extensive overview of all contemplated aspects,and is intended to neither identify key or critical elements of allaspects nor delineate the scope of any or all aspects. Its purpose is topresent some concepts of one or more aspects in a simplified form as aprelude to the more detailed description that is presented later.

In one aspect, the disclosure provides a method for fabricating anobject. The method includes: (a) irradiating a layer of powder in apowder bed with an energy beam in a series of scan lines to form a fusedregion; (b) providing a subsequent layer of powder over the powder bedby passing a recoater arm over the powder bed from a first side of thepowder bed to a second side of the powder bed; and (c) repeating steps(a) and (b) until the object and at least one support structure isformed in the powder bed. The at least one support structure includes aplurality of substantially parallel vertical walls, each wall extendingsubstantially parallel to a direction from the first side to the secondside. Adjacent walls of the plurality of substantially parallel verticalwalls are separated by a portion of unfused powder. The object is formedabove the plurality of substantially parallel vertical walls.

In another aspect, the disclosure provides a method of fabricating anobject based on a three dimensional computer model including the objectand a solid support structure under the object. The method uses amanufacturing apparatus including a powder bed, energy beam, and arecoater arm. The method includes scanning multiple scan lines of thesolid support in the powder bed in a single direction substantiallyparallel to a direction of movement of the recoater arm using a beamwidth less than a spacing between adjacent scan lines. The method alsoincludes scanning multiple scan lines of the object above the supportstructure using a beam width greater than the spacing between adjacentscan lines.

These and other aspects of the invention will become more fullyunderstood upon a review of the detailed description, which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is schematic diagram showing an example of a conventionalapparatus for additive manufacturing.

FIG. 2 illustrates a plan view of an example object and a conventionalmatrix support.

FIG. 3 illustrates a perspective view of an example of a rectangularprism object supported by a support structure including rail supports inaccordance with aspects of the present disclosure.

FIG. 4 illustrates a front view of the rectangular prism object andexample support structure in FIG. 3.

FIG. 5 illustrates side view of the rectangular prism object and examplesupport structure in FIG. 3.

FIG. 6 illustrates a perspective view of an example of a cylindricalobject supported by a support structure in accordance with aspects ofthe present invention.

FIG. 7 illustrates a front view of the cylindrical object and examplesupport structure in FIG. 6.

FIG. 8 illustrates side view of the cylindrical object and examplesupport structure in FIG. 6.

FIG. 9 illustrates horizontal cross-sectional view of the cylindricalobject and example support structure in FIG. 6.

FIG. 10 illustrates a vertical cross-sectional view of another exampleobject and support structure.

FIG. 11 illustrates a horizontal cross-sectional view of the object andsupport structure in FIG. 10.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appendeddrawings is intended as a description of various configurations and isnot intended to represent the only configurations in which the conceptsdescribed herein may be practiced. The detailed description includesspecific details for the purpose of providing a thorough understandingof various concepts. However, it will be apparent to those skilled inthe art that these concepts may be practiced without these specificdetails. In some instances, well known components are shown in blockdiagram form in order to avoid obscuring such concepts.

FIGS. 3-5 illustrate an example of a rectangular prism object 300supported by a support structure 310 in accordance with aspects of thepresent invention. FIG. 3 is a perspective view of the rectangular prismobject 300 and the support structure 310. FIG. 4 is a front view of therectangular prism object 300 and the support structure 310. FIG. 5 is anend view of the rectangular prism object 300 and the support structure310.

The rectangular prism object 300 and the support structure 310 may bemanufactured according to an AM process. For example, the apparatus 100of FIG. 1 and method described above may be used. In this type of AMprocess, the object 300 is built layer-by-layer by selectively sinteringor melting areas of the powder in the regions that form the object 300.The support structure 310 is built simultaneously with the object 300 bymelting or sintering additional regions of the powder in the location ofthe support structure 310.

Upon completion of the AM process, the support structure 310 is removedfrom the object 300. In one aspect, the support structure 310 isattached along with the object to the build plate and may be detachedfrom the build plate and discarded. The support structure 310 mayalternatively be formed without attachment to the build plate as a freestanding object within the powder bed. For example, the supportstructure 310 may be formed on top of a first portion of an object inorder to support an overhanging second portion of the object. Inaddition, the support structure 310 may be attached to the object 300along each of the rails 312, which may be readily broken away once theAM process is complete. This may be accomplished by providing abreakaway structure—a small tab of metal joining the object 300 andsupport structure 310. The breakaway structure may also resemble aperforation with several portions of metal joining the object 300 andsupport structure 310.

The removal of the support structure 310 from the object 300 may takeplace immediately upon, or during, removal of the object from the powderbed. Alternatively, the support structure may be removed after any oneof the post-treatment steps. For example, the object 300 and supportstructure 310 may be subjected to a post-anneal treatment and/orchemical treatment and then subsequently removed from the object 300and/or build plate.

The present inventors have found that certain objects may benefit from asupport structure 310 that includes vertical walls or rails oriented ina direction substantially parallel to the recoater direction 134. In theexample aspect illustrated in FIGS. 3-5, the rectangular prism object300 is separated from the build plate 114. The object 300 may be, forexample, a tab protruding from a larger object.

The object 300 is generally a solid object or includes solid portions.The apparatus 100 forms the object 300 by melting a series ofoverlapping scan lines in each layer of the object 300. That is, whenforming a layer of the object 300, the galvo scanner scans a series ofparallel scan lines with the energy beam to melt the powder in a regionof the powder bed corresponding to the location of the object in thelayer. The width of the energy beam is set wider than the distancebetween the scan lines so that the melt pool formed by each scan linefuses with the adjacent scan line to form a solid layer. The beam widthmay be controlled directly, or may be set by adjusting a power of theenergy beam or a movement speed of the galvo scanner. The apparatus 100changes the orientation of the scan lines in successive layers in orderto provide uniform fusing. For example, rotating the orientation of thescan lines in successive layers helps prevent structural weaknesses fromdeveloping within the solid object 300.

The support structure 310 is a support structure including a pluralityof rails 312. Each rail 312 is a vertical wall oriented in a directionsubstantially parallel to the recoater direction 134. The angle formedbetween each rail and the recoater direction 134 is less than 30degrees, preferably less than 10 degrees, and more preferably less than5 degrees. In one embodiment, the orientation of the rails is alignedwith the recoater direction 134 such that the orientation of the railsis parallel to the recoater direction 134. Although the rails 312 areillustrated as aligned with the sides of the object 300, in an aspect,the orientation of the rails 312 is independent of the shape andorientation of the object 300. Each rail 312 extends vertically from thebuild plate 114 to a bottom surface of the object 300. The adjacentrails 312 are separated by a continuous portion of unfused powder. In anaspect, the portion of unfused powder has a minimum width sufficient toprevent the adjacent rails 312 from fusing together. In an aspect, theminimum width separating the adjacent rails 312 is based on thermalproperties of the powder. The minimum width is sufficient to prevent theunfused powder from sintering due to heat from the rails 312. In anaspect, the minimum width is between 0.1 millimeters to 10 millimeters,preferably approximately 1 millimeter. In an aspect, there are no fusedportions connecting adjacent rails 312.

The rails 312 are formed layer by layer by fusing a line of powder atthe same location in each subsequent layer. As the recoater 116 providesa subsequent layer of powder on top of the newly fused top layer of therails 312, the recoater 116 moves in a direction substantially parallelto each of the rails 312. In an aspect, the thickness of a subsequentlayer may be in the range of approximately 20 microns to approximately50 microns. Due to warping or other thermal expansion or contraction, itis possible for recoater 116 to contact the rails 312. Due to thesubstantially parallel orientation of the rails with respect to themovement of the recoater 116, even if recoater 116 contacts the rails312, the recoater 116 will generally ride on top of the rails 312 ratherthan exerting lateral forces against the narrow dimension of the rails312. Further, the portion of unfused powder between the rails 312 maymove in response to lateral forces generated by movement of the powderas the recoater 116 provides the subsequent layer. For example, theportion of unfused powder may shift or compress in a direction parallelto the recoater direction 134. Because there are no surfaces of therails 312 transverse to the recoater direction 134, the movement of thepowder does not apply significant lateral forces to the supportstructure 310. Accordingly, the support structure 310 may be less likelyto deform or tip over, which could result in a failed build or adefective object 300.

In an aspect, the apparatus 100 forms the support structure 310 based ona three dimensional computer model including an individual object foreach rail 312. Using a CAD program, the operator modifies a threedimensional model of the object to include the additional objects foreach rail. The operator may use software to generate multiple objectswithin the three dimensional model. The three dimensional model is thenprovided to the apparatus 100. The apparatus 100 forms each rail 312 asa separate solid object. Each rail 312 may be formed by a single scanline.

In another aspect, the support structure 310 is defined as a singlesolid object within the three dimensional model. For example, theoperator uses the CAD program to extrude the object 300 downward. Anextrude function is typically available in the CAD program. The extrudefunction determines the coordinates of the edges of a bottom surface ofthe object and generates a second object extending downward from theobject to a point such as another solid object or the bottom of themodel (e.g., the build plate) as designated by the operator. Forexample, for the object 300, the coordinates of the edges of the bottomsurface are defined by the four corners. Accordingly, the extrudedobject corresponding to the support structure 310 is also a rectangularprism. In the three dimensional model, the support structure 310 is asolid object. When the three dimensional model is provided to theapparatus 100, the operator sets the scan parameters for the supportstructure 310 such that the rails 312 are formed instead of a solidblock. Each rail 312 is formed by a single scan line. A width of theenergy beam is set to be less than a distance between center lines ofthe rails 312. The spacing between scan lines is set equal to thedistance between the center lines of the rails 312. Additionally, aconstant direction for the scan lines is set for the support structure310. The constant direction is substantially parallel to the recoaterdirection 134. The scan lines may be formed as the galvo scanner 132scans either forward or backward along the recoater direction 134. Theconstant direction does not change between layers, so the scan lines ineach subsequent layer are aligned with the scan lines in the layer belowto form the rails 312.

FIGS. 6-9 illustrate an example of a cylindrical object 600 supported bya support structure 610 in accordance with aspects of the presentinvention. FIG. 6 is a perspective view of the cylindrical object 600and the support structure 610. FIG. 7 is a front view of the cylindricalobject 600 and the support structure 610. FIG. 8 is an end view of thecylindrical object 600 and the support structure 610. FIG. 9 is ahorizontal cross sectional view of the cylindrical object 600 and thesupport structure 610.

Similar to the object 300 discussed above, The object 600 is a solidobject formed by melting a series of overlapping scan lines in eachlayer. The apparatus 100 changes the orientation of the scan lines insuccessive layers in order to provide uniform fusing. The supportstructure 610 is a support structure including a plurality of rails 612.Each rail 612 is a vertical wall oriented in a direction parallel to therecoater direction 134. The rails 612 may have similar spacing to therails 312 discussed above.

The apparatus 100 may also form the rails 612 based on a threedimensional model.

Generating individual rails 612 with a CAD program may be tediousbecause each rail 612 has a different height corresponding to the bottomsurface of the object 600. The rails 612 may also be generated byextruding the object 600 downward. Because the object 600 does not havea flat bottom surface, the object 600 may be extruded downward from itswidest point. Accordingly, the coordinates forming the edges of theextruded object are based on the sides and ends of the cylindricalobject 600. The extruded object has a rectangular horizontal crosssection, but the vertical cross section has a concave upward top surfacecorresponding to the bottom surface 602 of the object 600. When thethree dimensional model of the object 600 and the extruded object isprovided to the apparatus 100, the operator sets the scan parameters forthe support structure 610 such that the rails 612 are formed instead ofa solid block. Each rail 612 is formed by a single scan line. A width ofthe energy beam is set to be less than a distance between center linesof the rails 612. The spacing between scan lines is set equal to thedistance between the center lines of the rails 612. Additionally, aconstant direction for the scan lines is set for the support structure610. The constant direction is parallel to the recoater direction 134.The scan lines may be formed as the galvo scanner 132 scans eitherforward or backward along the recoater direction 134. The constantdirection does not change between layers, so the scan lines in eachsubsequent layer are aligned with the scan lines in the layer below toform the rails 612.

As illustrated in FIG. 9, as the object 600 and the support structure610 are being formed, a horizontal layer may include portions of boththe object 600 and the support structure 610. The portion of the supportstructure 610 includes adjacent rails 612 separated by a portion ofunfused powder 614. The galvo scanner 132 scans the portion of theobject 600 with different scan parameters than the scan parameters usedfor the portion of the support structure 610. For example, the width ofthe scan lines for the object 600 is wider and the distance between scanlines is narrower such that the scan lines overlap to form a solidobject. Additionally, the orientation of the scan lines may be changedwithin the layer or between layers to promote even melting. When therecoater 116 applies a subsequent layer of powder, the recoater travelsin a direction substantially parallel to the rails 612 as well astraveling over the portion of the solid object 600.

FIGS. 10 and 11 illustrate yet another example object 1000 and a supportstructure 1010. FIG. 10 illustrates a vertical cross section of theobject 1000 and the support structure 1010. FIG. 11 illustrates ahorizontal cross section of the object 1000 and the support structure1010. For FIG. 10, the recoater direction is into the page and for FIG.11, the recoater direction 134 is illustrated.

The object 1000 is a cylindrical object having an external flange 1002at one end. The object 1000 is oriented such that the axis of thecylindrical object is vertical and the flange 1002 is located at a topend. If no support structure were included, the flange 1002 would likelycause build errors because the relatively large bottom surface of theflange 1002 would be unsupported. As illustrated in FIG. 11, the object1000 may be formed by overlapping scan lines oriented in differentdirections.

The support structure 1010 includes a plurality of rails 1012. Asillustrated, each rail 1012 extends from the build plate 114 verticallyto the bottom surface of the flange 1002. Within each horizontal layer,as illustrated in FIG. 11, each rail 1012 extends horizontally to occupythe space beneath the flange 1002. The support structure 1010 is avertically oriented cylinder formed by a plurality of vertical railsoriented in a direction parallel to the recoater direction 134.

Moreover a method of fabricating an object may include consecutively,concurrently, or alternatingly, melting powder to form portions ofmultiple supports as described above. Additionally, for an objectfabricated using multiple supports, the post-processing procedures mayinclude removing each of the supports. In an aspect, a support structuremay include multiple supports of different types as described herein.The multiple supports may be connected to each other directly, or viathe object. The selection of supports for a specific object may be basedon the factors described herein (e.g., shape, aspect ratios,orientation, thermal properties, etc.).

When it becomes necessary to remove the support structure 310/610/1010from the object 300/600/1000, the operator may apply force to break thesupport structure free when contact surfaces are present. The supportstructure may be removed by mechanical procedures such as twisting,breaking, cutting, grinding, filing, or polishing. Additionally, thermaland chemical post processing procedures may be used to finish theobject. The removal of the support structure 310/610/1010 from theobject 300/600/1000 may take place immediately upon or during removal ofthe object from the powder bed. Alternatively, the support structure maybe removed after any one of the post-treatment steps. For example, theobject 300/600/1000 and support structure 310/610/1010 may be subjectedto a post-anneal treatment and/or chemical treatment and thensubsequently removed from the object 300/600/1000 and/or build plate.

In an aspect, multiple supports may be used in combination to supportfabrication of an object, prevent movement of the object, and/or controlthermal properties of the object. That is, fabricating an object usingadditive manufacturing may include use of one or more of: scaffolding,tie-down supports, break-away supports, lateral supports, conformalsupports, connecting supports, surrounding supports, keyway supports,breakable supports, leading edge supports, or powder removal ports. Thefollowing patent applications include disclosure of these supports andmethods of their use:

U.S. patent application Ser. No. 15/042,019, titled “METHOD ANDCONFORMAL SUPPORTS FOR ADDITIVE MANUFACTURING” with attorney docketnumber 037216.00008, and filed Feb. 11, 2016;

U.S. patent application Ser. No. 15/042,024, titled “METHOD ANDCONNECTING SUPPORTS FOR ADDITIVE MANUFACTURING” with attorney docketnumber 037216.00009, and filed Feb. 11, 2016;

U.S. patent application Ser. No. 15/041,973, titled “METHODS ANDSURROUNDING SUPPORTS FOR ADDITIVE MANUFACTURING” with attorney docketnumber 037216.00010, and filed Feb. 11, 2016;

U.S. patent application Ser. No. 15/042,010, titled “METHODS AND KEYWAYSUPPORTS FOR ADDITIVE MANUFACTURING” with attorney docket number037216.00011, and filed Feb. 11, 2016;

U.S. patent application Ser. No. 15/042,001, titled “METHODS ANDBREAKABLE SUPPORTS FOR ADDITIVE MANUFACTURING” with attorney docketnumber 037216.00012, and filed Feb. 11, 2016;

U.S. patent application Ser. No. 15/041,991, titled “METHODS AND LEADINGEDGE SUPPORTS FOR ADDITIVE MANUFACTURING” with attorney docket number037216.00014, and filed Feb. 11, 2016; and

U.S. patent application Ser. No. 15/041,980, titled “METHOD AND SUPPORTSWITH POWDER REMOVAL PORTS FOR ADDITIVE MANUFACTURING” with attorneydocket number 037216.00015, and filed Feb. 11, 2016.

The disclosure of each of these applications are incorporated herein intheir entirety to the extent they disclose additional support structuresthat can be used in conjunction with the support structures disclosedherein to make other objects.

Additionally, scaffolding includes supports that are built underneath anobject to provide vertical support to the object. Scaffolding may beformed of interconnected supports, for example, in a honeycomb pattern.In an aspect, scaffolding may be solid or include solid portions. Thescaffolding contacts the object at various locations providing loadbearing support for the object to be constructed above the scaffolding.The contact between the support structure and the object also preventslateral movement of the object.

Tie-down supports prevent a relatively thin flat object, or at least afirst portion (e.g. first layer) of the object from moving during thebuild process. Relatively thin objects are prone to warping or peeling.For example, heat dissipation may cause a thin object to warp as itcools. As another example, the recoater may cause lateral forces to beapplied to the object, which in some cases lifts an edge of the object.In an aspect, the tie-down supports are built beneath the object to tiethe object down to an anchor surface. For example, tie-down supports mayextend vertically from an anchor surface such as the platform to theobject. The tie-down supports are built by melting the powder at aspecific location in each layer beneath the object. The tie-downsupports connect to both the platform and the object (e.g., at an edgeof the object), preventing the object from warping or peeling. Thetie-down supports may be removed from the object in a post-processingprocedure.

A break-away support structure reduces the contact area between asupport structure and the object. For example, a break-away supportstructure may include separate portions, each separated by a space. Thespaces may reduce the total size of the break-away support structure andthe amount of powder consumed in fabricating the break-away supportstructure. Further, one or more of the portions may have a reducedcontact surface with the object. For example, a portion of the supportstructure may have a pointed contact surface that is easier to removefrom the object during post-processing. For example, the portion withthe pointed contact surface will break away from the object at thepointed contact surface. The pointed contact surface stills provides thefunctions of providing load bearing support and tying the object down toprevent warping or peeling.

Lateral support structures are used to support a vertical object. Theobject may have a relatively high height to width aspect ratio (e.g.,greater than 1). That is, the height of the object is many times largerthan its width. The lateral support structure is located to a side ofthe object. For example, the object and the lateral support structureare built in the same layers with the scan pattern in each layerincluding a portion of the object and a portion of the lateral supportstructure. The lateral support structure is separated from the object(e.g., by a portion of unmelted powder in each layer) or connected by abreak-away support structure. Accordingly, the lateral support structuremay be easily removed from the object during post-processing. In anaspect, the lateral support structure provides support against forcesapplied by the recoater when applying additional powder. Generally, theforces applied by the recoater are in the direction of movement of therecoater as it levels an additional layer of powder. Accordingly, thelateral support structure is built in the direction of movement of therecoater from the object. Moreover, the lateral support structure may bewider at the bottom than at the top. The wider bottom provides stabilityfor the lateral support structure to resist any forces generated by therecoater.

This written description uses examples to disclose the invention,including the preferred embodiments, and also to enable any personskilled in the art to practice the invention, including making and usingany devices or systems and performing any incorporated methods. Thepatentable scope of the invention is defined by the claims, and mayinclude other examples that occur to those skilled in the art. Suchother examples are intended to be within the scope of the claims if theyhave structural elements that do not differ from the literal language ofthe claims, or if they include equivalent structural elements withinsubstantial differences from the literal language of the claims.Aspects from the various embodiments described, as well as other knownequivalents for each such aspect, can be mixed and matched by one ofordinary skill in the art to construct additional embodiments andtechniques in accordance with principles of this application.

1. A method for fabricating an object, comprising: (a) irradiating alayer of powder in a powder bed with an energy beam in a series of scanlines to form a fused region; (b) providing a subsequent layer of powderover the powder bed by passing a recoater arm over the powder bed from afirst side of the powder bed to a second side of the powder bed; and (c)repeating steps (a) and (b) until the object and at least one supportstructure is formed in the powder bed, wherein the at least one supportstructure includes a plurality of substantially parallel vertical walls,each wall extending substantially parallel to a direction from the firstside to the second side; wherein adjacent walls of the plurality ofsubstantially parallel vertical walls are separated by a continuousportion of unfused powder; and wherein the object is formed above theplurality of parallel vertical walls.
 2. The method of claim 1, furthercomprising: setting a width of the energy beam to be less than adistance between center lines of the adjacent walls when irradiating thepowder forming the support structure.
 3. The method of claim 2, furthercomprising: setting a spacing between scan lines equal to the distancebetween center lines of the adjacent walls.
 4. The method of claim 2,further comprising: setting a constant orientation for the scan lineswithin the at least one support structure.
 5. The method of claim 1,further comprising: providing a three dimensional computer model of theobject; extruding, in a computer aided design program, the objectdownward to define the at least one support structure under the object;and providing the model of the object and the at least one supportstructure to an additive manufacturing apparatus.
 6. The method of claim5, wherein the additive manufacturing apparatus includes a processorexecuting a control program that controls the additive manufacturingapparatus to perform steps (a), (b), and (c) according to the model. 7.The method of claim 1, further comprising: providing a three dimensionalcomputer model of the object; adding, in a computer aided designprogram, a model of each of the plurality of parallel vertical walls;and providing the model of the object and the plurality of parallelvertical walls to an additive manufacturing apparatus.
 8. The method ofclaim 1, wherein a distance between center lines of the adjacent wallsis at least 1 millimeter.
 9. The method of claim 1, wherein a distancebetween center lines of the adjacent walls is between approximately 1millimeter and approximately 10 millimeters.
 10. The method of claim 1,wherein a width of each of the plurality of walls is approximately 0.5millimeters.
 11. The method of claim 1, wherein an angle formed betweenthe vertical walls and the direction from the first side to the secondside is less than 10 degrees.
 12. The method of claim 1, wherein theangle formed between the vertical walls and the direction from the firstside to the second side is less than 5 degrees.
 13. A method offabricating an object based on a three dimensional computer modelincluding the object and a solid support structure under the objectusing a manufacturing apparatus including a powder bed, energy beam, anda recoater arm, comprising: scanning multiple scan lines of the solidsupport in the powder bed in a single direction substantially parallelto a direction of movement of the recoater arm using a beam width lessthan a spacing between adjacent scan lines; and scanning multiple scanlines of the object above the support structure using a beam widthgreater than the spacing between adjacent scan lines.
 14. The method ofclaim 13, wherein a direction of the scan lines in the object changesbetween subsequent layers.
 15. The method of claim 13, wherein an angleformed between the single direction and the direction of movement of therecoater arm is less than 10 degrees.
 16. The method of claim 15,wherein the angle formed between single direction and the direction ofmovement of the recoater arm is less than 5 degrees.
 17. The method ofclaim 13, wherein scanning the multiple scan lines comprises irradiatinga layer of powder in the powder bed of the additive manufacturingapparatus with the energy beam according to the model to form a fusedregion.
 18. The method of claim 17, wherein the fused region forms theobject and the support structure including a plurality of substantiallyparallel vertical walls, each wall extending in the direction ofmovement of the recoater arm; and wherein adjacent walls of theplurality of substantially parallel vertical walls are separated by acontinuous portion of unfused powder.
 19. The method of claim 17,wherein the additive manufacturing apparatus includes a processorexecuting a control program that controls the additive manufacturingapparatus according to the model.
 20. The method of claim 13, whereinthe spacing between adjacent scan lines is at least 1 millimeter. 21.The method of claim 13, wherein a distance between adjacent scan linesis between approximately 1 millimeter and approximately 10 millimeters.22. The method of claim 13, wherein the beam width is approximately 0.5millimeters.
 23. The method of claim 13, further comprising setting scanparameters of the additive manufacturing apparatus for the solid supportstructure to set the beam width to be less than the spacing betweenadjacent scan lines and to fix the direction of the scan lines to thedirection of movement of the recoater arm in multiple layers.